This invention relates generally to test instrument probes, and in particular to a combined test instrument probe and voltage detector.
Test instruments such as digital multimeters, analog volt-ohmmeters, oscilloscopes and the like are used to measure electrical parameters such as a.c. and d.c. voltages and currents. Test probes are used to connect test instruments to electrical or electronic circuits so that measurements may be made. A problem exists in situations where an instrument user connects a probe to a potentially dangerous a.c. voltage source and gets no reading when in fact a high voltage is present. This non-reading situation may arise from broken or disconnected test leads, broken a.c. receptacles, or even when the test instrument is in a different measuring mode from that intended. Incorrect readings or an indication that no voltage is present when in fact a dangerous voltage exists may create a dangerous situation for the user relying on the instrument.
Both noncontacting voltage detectors and contacting voltage detectors are well known in the art, and are often referred to as continuity checkers, light pens, volt sticks or wands, or leadless voltage probes. U.S. Pat. No. 3,919,631 issued Nov. 11, 1975, to Brown, and U.S. Pat. No. 5,103,165, issued Apr. 7, 1992, to Siratz, disclose similar noncontacting voltage detectors. U.S. Pat. No. 4,006,409 issued Feb. 1, 1977, to Adams discloses a contacting voltage detector. While quite useful, these devices are easily lost because of their small size, or are simply forgotten when a technician takes a test instrument to measure an electrical circuit.